His elder brother Warren adds: “Lewis was just an immaculate conception. I remember my dad had a vasectomy and then nine months later we got a surprise with Lewis popping out.”

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Lewis's ex girlfriend Paige Turley went on to win the winter series of Love Island earlier this yearCredit: Getty Images - Getty

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Lewis wrote emotional ballad Hold Me While You Wait about ex Paige

The short YouTube film, called Birthday Song and released today, sees Lewis reflect on growing up in Glasgow, where he wrote emotional ballads including Hold Me While You Wait, inspired by ex-girlfriend and Love Island winner Paige Turley, that turned him into a most unlikely chart topper.

He also performs a couple of covers by his heroes Oasis and The Chemical Brothers. Setting Sun by The Chemical Brothers was No1 when he was born.

Lewis says his love affair with music began in his family car, a Renault Espace his parents drove from his home in Glasgow to France on holiday, taking Lewis, elder brothers Aidan and Warren and sister Danielle.

Lewis was obsessed with a Queen CD his folks had played on the way. So much so that he performed We Are The Champions at a holiday talent show.

Middle brother Aidan said: “That’s probably what started him off. Wanting all the attention. That’s when we knew he was gonna make it, he’s a born attention seeker.”

But it would be his eldest brother Warren, not his parents, who would have the most influence on Lewis in terms of music.

But it’s clear to see where he got his sense of humour from.

Lewis says: “None of my parents played in bands. My mum is tone deaf. My dad was in a play once in school . . . for one day. And he always likes to bring it up. He says, ‘That’s where you get it from’.

“My brother was the first one to pick it up. He’s six years older than me so he started playing in bands and stuff when I was about nine.”

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Lewis started performing and playing guitar to emulate his older brother

Aidan adds: “He wanted to do what his older brother was doing. His older brother was writing songs, he went, ‘Cool, I need to write songs’.

His older brother was singing songs, ‘All right, I need to sing’. Everything Lewis went on to do is all from wanting to be like his older brother.”

Warren jokes he should be owed a slice of Lewis’s £7.8million fortune, which he’s bagged over the past year through record sales and touring.

He says: “It makes me feel like I should be getting a cut from his royalties if I’ve influenced him that much.”

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Lewis said he 'spent a lot of time bored' as a teen which may have contributed to him picking up an instrument

Lewis had plenty of time to pick up the guitar and sing in Whitburn, West Lothian, on the outskirts of Glasgow, where there wasn’t much to do. He says: “We moved from Glasgow when I was four or five to Whitburn.

“It was actually a very nice place to grow up, I think. Just regular. There was a park, had a couple of swings. There was not much gang violence, thank God.

“I spent a lot of time bored. And a lot of time doing nothing. That might have helped contribute to me picking up an instrument.

“Being the youngest you learn from your brothers’ and sister’s mistakes.

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Lewis with his older brothers Warren and Aidan and sister Dani

“They did this and they got in trouble for that or they did that . . . So if my brother went out drinking when he was too young he would get a b******ing for that.”

His natural talent for seeking attention was increasingly evident during music classes at school.

Lewis says: “I remember there was a guitar club in primary seven, the teacher was Miss Weatherstone. I thought I was class. And then it gets to me and I’m like, ‘Yeessss, you are all s***e’.

"And the bass player of my band now, a guy called Aidan Beattie, played Live Forever by Oasis and sang it at the same time. I was like, ‘You b******, I want to know how to do that’.”

Class clown

Describing school pal Lewis, who he met at St Joseph’s Primary School in Whitburn, Aidan says: “A funny guy, a joker, a class clown, definitely. He’s just the exact same. He hasn’t changed a bit really.”

Lewis adds: “I remember it being fun. I don’t remember doing any work. I remember one time a guy made up a filthy language and it was like, baseball bat meant penis, spaghetti meant pubes. And the f***ing b****** dobbed me in it and said I did it with him.

“I f***ing never and I’m standing there like, ‘Who the f*** is this?’ I cried so hard. And I was like, ‘I didn’t mean it, I never wrote monster truck’, which meant my left b****** or something.”

The pair would play together for the first time in a school talent show — and were a hit.

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Lewis got his start performing in a school talent show with his friend AidanCredit: The Mega Agency

Lewis says: “We sang Live Forever together and we won the f***er. And yeah that’s the first song I think I learnt to play and sing at the same time. And I got a bug from it.”

Their teacher, Mrs Mooney, says: “Everybody loved it and the two boys sat in front of the stage and just played away and it was quite emotional and overwhelming.”

The duo progressed to playing regular slots at their local pub, The Grand but Lewis was far, far from an instant success.

He says: “People were playing U2 songs, the Beatles. And then two wee 14-year-olds go up saying, ‘We’re gonna play you a song that was written by me’. And people hated it, people hated us, they thought we were s***e.”

'He stuck out clearly'

His bandmate Adam Warrington, who performed alongside Lewis in his teens, told how he persevered until he won over the audience.

Adam says: “He spent a long time trying to develop this song-making craft and then one day I think he really hit the nail on the head. Everyone absolutely loved it.”

Landlord of The Grange, David Goldie, recalls: “I remember the very first time I heard Lewis sing.

"It feels like a long time ago but he stuck out clearly. He had a tone and a sound that was different to most pub bands or pub acts.